Zonal Isolation Systems For Subterranean Wells

ABSTRACT

A zonal isolation system for a subterranean well comprises at least one tubular body that comprises at least one semi-permeable membrane, or at least one removable material or both. The semi-permeable membrane is permeable to one or more activators that may cause a cement slurry to begin setting. The tubular body may comprise openings that are covered by or filled with a removable material. After a primary cementing treatment has been completed, the activator may be introduced into the tubular body, whereupon it passes through the tubular body and out into the cement slurry.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

This disclosure relates to compositions and methods for treating subterranean formations, in particular, compositions and methods for providing zonal isolation and cementing subterranean wells.

During the construction of subterranean wells, it is common, during and after drilling, to place a tubular body in the wellbore. The tubular body may comprise drillpipe, casing, liner, coiled tubing or combinations thereof. The purpose of the tubular body is to act as a conduit through which desirable fluids from the well may travel and be collected. The tubular body is normally secured in the well by a cement sheath. The cement sheath provides mechanical support and hydraulic isolation between the zones or layers that the well penetrates. The latter function is important because it prevents hydraulic communication between zones that may result in contamination. For example, the cement sheath blocks fluids from oil or gas zones from entering the water table and polluting drinking water. In addition, to optimize a well's production efficiency, it may be desirable to isolate, for example, a gas-producing zone from an oil-producing zone. The cement sheath achieves hydraulic isolation because of its low permeability. In addition, intimate bonding between the cement sheath and both the tubular body and borehole is necessary to prevent leaks.

The cement sheath is usually placed in the annular region between the outside of the tubular body and the subterranean borehole wall by pumping the cement slurry down the interior of the tubular body, out the bottom and up into the annulus. The cement slurry may also be placed by the “reverse cementing” method, whereby the slurry is pumped directly down into the annular space. During the cementing process, the cement slurry is frequently preceded by a spacer fluid or chemical wash to prevent commingling with drilling fluid in the wellbore. These fluids also help clean the tubular-body and formation surfaces, promoting better cement bonding and zonal isolation. The cement slurry may also be followed by a displacement fluid such as water or a brine. This fluid usually resides inside the tubular body after the cementing process is complete. A complete description of the cementing process is presented in the following publication. Piot B and Cuvillier G: “Primary Cementing Techniques,” in Nelson EB and Guillot D: Well Cementing—2nd Edition, Houston, Schlumberger (2006) 459-501.

Optimal cement-sheath placement often requires that the cement slurry contain additives that adjust the slurry's physical characteristics or performance. For example, retarders extend the available pumping time (or thickening time) before the slurry begins to set. Conversely, accelerators shorten the available pumping time. Ideally, the cement slurry would begin to set just after placement, thereby shortening idle rig time and reducing operating costs. However, if the cement slurry begins to set prematurely, a situation may arise wherein the cement slurry becomes unpumpable before it has been placed properly in the annulus. Such a condition is called “CLIP”. CLIP is an acronym for “cement left in pipe,” when the cement slurry has not been completely evacuated from the interior of the tubular body. When CLIP occurs, the cement slurry may fail to completely fill the annular space, resulting in compromised zonal isolation. Furthermore, the well operator will most likely have to drill the cement out of the tubular-body interior.

Sometimes, the cementing process involves a very long tubular body, and the temperature at the shallowest point of the tubular body is significantly lower than that at the deepest point of the tubular body. Under these circumstances the setting time at the shallowest point may be much longer than that at the deepest point. As a result, the operator may have to wait a longer than desired time for the entire cement sheath to set—a long waiting-on-cement (WOC) time. This extra time may be costly in terms of rig- and personnel time.

The dosage of accelerators or retarders in a cement slurry depends mainly on the well temperature and the anticipated placement time. After the slurry has been prepared at surface and begins its journey into the well, the well operator must usually rely on the additives to perform properly. Very little may be done to influence cement-slurry performance after placement has commenced.

Therefore, despite the valuable contributions of the prior art, it would be desirable for well operators to have additional means to control the performance of the cement slurry during and after placement. Optimally, the setting time could be controlled such that the cement slurry reaches its intended destination, and then the slurry could be triggered to promptly begin setting and providing zonal isolation.

SUMMARY

In the present disclosure, means are provided to allow a well operator to trigger the setting of a cement slurry following placement.

In an aspect, embodiments relate to zonal isolation systems.

In a further aspect, embodiments relate to methods for establishing zonal isolation in a subterranean wellbore.

In yet a further aspect, embodiments relate to methods for cementing a subterranean wellbore.

DETAILED DESCRIPTION

At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The description and examples are presented solely for the purpose of illustrating the preferred embodiments should not be construed as a limitation to the scope and applicability of the disclosed embodiments. While the compositions of the present disclosure are described herein as comprising certain materials, it should be understood that the composition could optionally comprise two or more chemically different materials. In addition, the composition can also comprise some components other than the ones already cited.

The Applicant has surprisingly discovered that the setting of a cement slurry may be triggered by exposing it to a chemical activator after placement. The activator is preferably transferred from within the tubular body, through the tubular body, and out into the cement slurry.

Embodiments relate to zonal isolation systems. The systems may comprise (a) at least one tubular body that comprises at least one semi-permeable membrane; or (b) at least one semi-permeable membrane covered by a removable material; or (c) at least one opening covered by or filled with a removable material, or both; or (d) a combination thereof. The tubular body may allow an activator to pass from within the tubular body, through the tubular body and out of the tubular body, thereby contacting a cement slurry and causing it to begin setting.

The activator may comprise one or more members of sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, sodium aluminate, iron (II) and iron (III) salts, polyacrylic acid salts, calcium chloride, calcium nitrate, calcium acetate, calcium nitrite, calcium formate, thiocyanate salts and triethanolamine. The semi-permeable membrane in the tubular body is preferably permeable to one or more of the aforementioned activators.

The semi-permeable membrane may be present throughout the length of the tubular body, or at strategic points along the tubular body. The semi-permeable membrane may be further coated by a removable material, the removable material offering protection during the placement of the tubular body into the well, and the primary cementing process. The semi-permeable membrane may also be transparent to electromagnetic radiation, allowing the operator to perform logging operations or to heat the cement slurry by applying for example microwaves.

The tubular body may comprise at least one opening or hole through which an activator may pass. Openings may be present throughout the length of the tubular body, or at strategic points along the tubular body. In such cases, the openings are preferably covered by or filled with a removable material, or both, preventing premature passage of materials through the openings during the placement of the tubular body into the well, and the primary cementing process.

Suitable removable materials may comprise one or more members of aluminum metal, iron metal, zinc metal, nickel metal, tin metal, paraffin wax and degradable polymers such as (but not limited to) polylactic acid, polyglycolic acid and polyester.

Embodiments relate to methods for establishing zonal isolation in a subterranean wellbore having a formation wall. A zonal isolation system is inserted into the wellbore that comprises (a) at least one tubular body that comprises at least one semi-permeable membrane; or (b) at least one semi-permeable membrane covered by a removable material; or (c) at least one opening covered by or filled with a removable material, or both; or (d) a combination thereof.

The tubular body may allow an activator to pass from within the tubular body, through the tubular body and out of the tubular body. A cement slurry is placed in the annular region between the outer surface of the tubular body and the formation wall. A fluid is then introduced inside the tubular body that comprises one or more activators. The fluid may pass from within the tubular body, through the tubular body and out of the tubular body, thereby contacting the cement slurry and causing it to begin setting.

The activator may comprise one or more members of sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, sodium aluminate, iron (II) and iron (III) salts, polyacrylic acid salts, calcium chloride, calcium nitrate, calcium acetate, calcium nitrite, calcium formate, thiocyanate salts and triethanolamine. The semi-permeable membrane in the tubular body would be preferably permeable to one or more of the aforementioned activators.

The semi-permeable membrane may be present throughout the length of the tubular body, or at strategic points along the tubular body. The semi-permeable membrane may be further coated by a removable material, the removable material offering protection during the placement of the tubular body into the well, and the primary cementing process. The semi-permeable membrane may also be transparent to electromagnetic radiation, allowing the operator to perform logging operations or to heat the cement slurry by applying microwaves.

The tubular body may comprise at least one opening or hole through which an activator may pass. Openings may be present throughout the length of the tubular body, or at strategic points along the tubular body. In such cases, the openings are preferably covered by or filled with a removable material, or both, preventing premature passage of materials through the openings during the placement of the tubular body into the well, and the primary cementing process.

Suitable removable materials may include one or more members of aluminum metal, iron metal, zinc metal, nickel metal, tin metal, paraffin wax and degradable polymers such as (but not limited to) polylactic acid, polyglycolic acid and polyester. When the disclosed tubular body incorporates a removable material, the pH of the activator fluid is preferably lower than 7, more preferably below 4 and most preferably below 2. In addition, the activator concentration in the fluid may preferably be higher than about 10 wt %, more preferably higher than about 30 wt % and most preferably higher than about 50 wt %.

The activator fluid may be introduced into the tubular-body interior by using it as a displacement fluid pumped behind the cement slurry. Or, the activator may be injected inside the tubular body at one or more strategic points. This limited injection may be accomplished by pumping the activator fluid through coiled tubing run inside the tubular body or by using other injection devices known by those skilled in the art.

Embodiments relate to methods for establishing zonal isolation in a subterranean wellbore having a formation wall. A zonal isolation system is inserted into the wellbore that comprises (a) at least one tubular body that comprises at least one semi-permeable membrane; or (b) at least one semi-permeable membrane covered by a removable material; or (c) at least one opening covered by or filled with a removable material, or both; or (d) a combination thereof.

The tubular body may allow an activator to pass from within the tubular body, through the tubular body and out of the tubular body. A cement slurry is placed in the annular region between the outer surface of the tubular body and the formation wall. A fluid is then introduced inside the tubular body that comprises one or more activators. The fluid may pass from within the tubular body, through the tubular body and out of the tubular body, thereby contacting the cement slurry and causing it to begin setting.

The activator may comprise one or more members of sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, sodium aluminate, iron (II) and iron (III) salts, polyacrylic acid salts, calcium chloride, calcium nitrate, calcium acetate, calcium nitrite, calcium formate, thiocyanate salts and triethanolamine. The semi-permeable membrane in the tubular body would be preferably permeable to one or more of the aforementioned activators.

The semi-permeable membrane may be present throughout the length of the tubular body, or at strategic points along the tubular body. The semi-permeable membrane may be further coated by a removable material, the removable material offering protection during the placement of the tubular body into the well, and the primary cementing process. The semi-permeable membrane may also be transparent to electromagnetic radiation, allowing the operator to perform logging operations or to heat the cement slurry by applying microwaves.

The tubular body may comprise at least one opening or hole through which an activator may pass. Openings may be present throughout the length of the tubular body, or at strategic points along the tubular body. In such cases, the openings are preferably covered by or filled with a removable material, or both, preventing premature passage of materials through the openings during the placement of the tubular body into the well, and the primary cementing process.

Suitable removable materials may include one or more members of the list consisting of aluminum metal, iron metal, zinc metal, nickel metal, tin metal, paraffin wax and degradable polymers such as (but not limited to) polylactic acid, polyglycolic acid and polyester. When the disclosed tubular body incorporates a removable material, the pH of the activator fluid is preferably lower than 7, more preferably below 4 and most preferably below 2. In addition, the activator concentration in the fluid may preferably be higher than about 10 wt %, more preferably higher than about 30 wt % and most preferably higher than about 50 wt %.

The activator fluid may be introduced into the tubular-body interior by using it as a displacement fluid pumped behind the cement slurry. Or, the activator may be injected inside the tubular body at one or more strategic points. This limited injection may be accomplished by pumping the activator fluid through coiled tubing run inside the tubular body or by using other injection devices known by those skilled in the art. 

1. A zonal isolation system for a subterranean well, comprising at least one tubular body that comprises: (i) at least one semi-permeable membrane; or (ii) at least one semi-permeable membrane covered by a removable material; or (iii) at least one opening covered by or filled with a removable material, or both; or (iv) a combination thereof.
 2. The system of claim 1, wherein the semi-permeable membrane is permeable to one or more activators in the list comprising sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, sodium aluminate, iron (II) and iron (III) salts, polyacrylic acid salts, calcium chloride, calcium nitrate, calcium acetate, calcium nitrite, calcium formate, thiocyanate salts and triethanolamine.
 3. The system of claim 1, wherein the semi-permeable membrane is transparent to electromagnetic radiation.
 4. The system of claim 1, wherein the removable material comprises one or more members of aluminum metal, iron metal, zinc metal, nickel metal, tin metal, polylactic acid, polyglycolic acid, polyester and paraffin wax.
 5. A method for establishing zonal isolation in a subterranean wellbore having a formation wall, comprising: (i) inserting a zonal isolation system in the wellbore, the system comprising (a) at least one semi-permeable membrane; or (b) at least one semi-permeable membrane covered by a removable material; or (c) at least one opening covered by or filled with a removable material, or both; or (d) a combination thereof; (ii) placing a cement slurry in the annular region between the outer surface of the tubular body and the formation wall; and (iii) introducing a fluid inside the tubular body that comprises one or more activators.
 6. The method of claim 5, wherein the semi-permeable membrane is permeable to one or more activators in the list comprising sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, sodium aluminate, iron (II) and iron (III) salts, polyacrylic acid salts, calcium chloride, calcium nitrate, calcium acetate, calcium nitrite, calcium formate, thiocyanate salts and triethanolamine.
 7. The method of claim 5, wherein the activator concentration in the fluid is higher than about 10 weight percent.
 8. The method of claim 5, wherein the semi-permeable membrane is transparent to electromagnetic radiation.
 9. The method of claim 5, wherein the removable material comprises one or more members of aluminum metal, iron metal, zinc metal, nickel metal, tin metal, polylactic acid, polyglycolic acid, polyester and paraffin wax.
 10. The method of claim 5, wherein the pH of the fluid is lower than
 7. 11. The method of claim 5, wherein the fluid is a displacement fluid.
 12. The method of claim 5, wherein the fluid is introduced at one or more strategic locations in the tubular body.
 13. A method for cementing a subterranean wellbore having a formation wall, comprising: (i) inserting a zonal isolation system in the wellbore, the system comprising (a) at least one semi-permeable membrane; or (b) at least one semi-permeable membrane covered by a removable material; or (c) at least one opening covered by or filled with a removable material, or both; or (d) a combination thereof; (ii) placing a cement slurry in the annular region between the outer surface of the tubular body and the formation wall; and (iii) introducing a fluid inside the tubular body that comprises one or more activators.
 14. The method of claim 13, wherein the semi-permeable membrane is permeable to one or more activators in the list consisting of: sodium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, sodium aluminate, iron (II) and iron (III) salts, polyacrylic acid salts, calcium chloride, calcium nitrate, calcium acetate, calcium nitrite, calcium formate, thiocyanate salts and triethanolamine.
 15. The method of claim 13, wherein the activator concentration in the fluid is higher than about 10 weight percent.
 16. The method of claim 13, wherein the semi-permeable membrane is transparent to electromagnetic radiation.
 17. The method of claim 13, wherein the removable material is one or more members of the list comprising aluminum metal, iron metal, zinc metal, nickel metal, tin metal, polylactic acid, polyglycolic acid, polyester and paraffin wax.
 18. The method of claim 13, wherein the pH of the fluid is lower than
 7. 19. The method of claim 13, wherein the fluid is a displacement fluid.
 20. The method of claim 13, wherein the fluid is introduced at one or more strategic locations in the tubular body. 